1. Field of Invention
This invention relates to gaskets employed in vehicles, and particularly to metallic gaskets employed in manifold exhaust systems of vehicles.
2. Description of the Prior Art
Exhaust manifolds used in automotive vehicles are subject to great variations in temperature, as well as to extreme mechanical vibrations. As such, the gaskets associated with exhaust manifolds and vehicle exhaust systems are known to present difficult sealing challenges. Gaskets interposed between exhaust connection parts are required to maintain resilient sealing properties over extended periods of time, and have an accompanying risk of exposing vehicular occupants to carbon monoxide poisoning if such gasket seals are inadequate.
Choices of gasket materials used under such severe conditions include metal-covered gaskets with soft core members such as heat resistant fibers including asbestos and ceramic fibers. More recently the use of expanded graphite and/or mica covered by a metallic sheet has been popular. Such metal-covered gaskets have provided relatively soft core members that offer excellent heat resistance, while the metallic coverings offer rigidity. However, such gaskets have been subject to reduction of contact pressure between connected parts over a period of time, along with deterioration of sealing properties under conditions of cyclic thermal expansion and vibrations, and thus recovery properties of such composite material bodies have not held up over time. In addition, graphite fillers used in such gaskets have been subject to severe oxidation, which compromises integrity of the gasket structures.
Spiral-wound gaskets have been offered to overcome issues of resiliency, hence recovery, as well as oxidation. However, most such spiral-wound gaskets have been formed of complex structures, which are expensive to manufacture. As a result, such gaskets have not been feasible for many applications.
The present invention provides a new improved gasket assembly that is simpler in construction, and relatively less expensive to manufacture than spiral-wound gaskets of the prior art. The improved gasket of this invention employs a spiral-wound plurality of tightly bound-together windings comprising a core or filler portion. The core windings present a Chevron cross-section, intermittently spot welded along its inside and outside circumferential diameters to define an integral pre-formed circular hoop. In a preferred embodiment, the core is formed of a stainless steel material. The core is covered by an outer circumferential metal wrap that is somewhat softer than the resilient, springy metal material of the core. In its preferred form, the outer wrap also comprises a metal of stainless steel, and entirely covers the exterior surfaces of the core to avoid oxidation.